Composite signaling system



H. S. OSBORNE.

COMPOSITE SIGNALING SYSTEM.

APPLICATION FILED FEB. 12, 1919.

k ES RQ R I N VEN TOR. 15'. 5. 05501726 BY E EN ERN W ATTORNEY UNITED STATES PATENT OFFICE.

HAROLD S. OSBORNE, OF NEW YORK, N. Y;, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

COMPOSITE SIGNALING SYSTEM.

To all whom it may concern:

Be it known that I, HAROLD S. OSBORNE, residing at New York, in the county of New York and State of New York, have invented certain Improvements in Composite Signaling Systems, of which the following is a specification.

. This invention ,relates to signaling systems, and especially those in which telegraphic currents of the same order of mag nitude as the telephone currents. It is the object of the present invention to provide a circuit of this character so designed as to reduce to the minimum interference between the signaling currents in the various channels and in particular between the telephone and telegraph channels. In the accompanying drawing the single figure illustrates diagrammatically a system embodying the invention. A 7

Two telephone circuits are indicated at 1 and 2 which may be the ordinary loaded linesemploying repeaters R R B For simplicity the repeaters for the side circuits only are shown. In actual practice repeaters for the phantom circuits would, of course, also be employed. These represent the two side circuits of a phantomed line 111 which the phantom circuit is produced in the usual manner by tapping the neutral points of transformers 3, as shown on the drawing. These telephone circuits may be either one way or two way circu ts so far as some features of the invention are concerned. Certain advantages inhere, however,.in making them one way circuits as will appear "hereinafter. If they are one way circuits, they will ordlnarlly, though not necessarily, be combined with other one way circuits,to form four-wlre circuits, or the equivalent, so that communication 1n either direction may be had.

Specification of Letters Patent.

Patented Apr. 12, 1921.

. Application filed February 12, 1919. Serial No. 276,486.

In the form of the invention here illustrated, the telegraphic channels also are shown as one way channels, the sending instruments belng ind cated at 4 at one end of the line, and-the receiving instruments at 5 at the other end of the line. One trans mitting and one receiving instrument is bridged. across each of the side circuits at opposite ends of the line, and each is of a character to provide a mid or neutral point 6. This is in order that a phantom telegraph channel can also be obtained by connecting the sending and receiving instru .ments across the neutral points at the respective ends of the line as indicated in the drawing. For this purpose the transmitting instruments may be of a form employing a single source of current, and a pole changer, with the impedance equally divided between the current source and the opposite sides of the line. The details of the transmitting device constitute no part of the present invention, being covered in a copending application. v

1 3 As is now well understood in the art, it is necessary to provide means for preventing the telephone currents from entering the telegraph branch of the circuit, and the telegraph currents from entering the telephone branch of the circuit. This is accomplished in the present instance by a high pass filter forfthe telephone branch, and a low pass filter for the telegraph branch, each of which serves. for both the side and phantom circuits of its respective branch. The high pass filter comprises capacities 7 arranged in seriesin either side of the tele phone branches, and inductances 8 and 8 connected in seriesacross conductors of each branch. These, when properly proportioned, operate in a known manner to suppress frequencies below a certain point, according to the manner in which they are tuned. In orderthat these elements may also serve as a high pass filter for the telephone phantom circuit, it is necessary that the shunt inductance in each branch be divided into two equalfparts 88 as above indicated, and these must be so disposed with respect to each other that they may have inductance effects which are independent as by placing the coils on separate cores. In this way a mid or neutral point in the inductive shunt across each branch is 5 provided, and'these points are connected, as

shown on the drawing, by a conductor 9.

In each of the telegraph branches connected to the side circuits, are located series inductances 10, the same number of like inductances being in each conductor of each branch. Across each branch circuit, and preferably between the sections of inductance, are connected capacities 11, each of which is composedof an even number of likeelements so as to provide mid or. neutral as Wellas for the'side circuits. The receiving end of the telegraph system is here illustrated as having a low pass filter of the same capacity as at thetransmitting end of the line. In many cases,'however, it will su'flice to have a simpler form of filter at this point; The filter at the sending end must servenot only to prevent injurious shunting of the telephone currents by the telegraph branches, but must also prevent the higher harmonics incident to the operation ofthe telegraph sender from reaching the telephoneline, as these would be of a frequency to interfere with telephone transmission. This difiiculty is not usually presentin the telegraph receiving apparatus.

By so arranglng the circuits as to provide for one way transmission of both the telegraph andtelephone currents over given wires, as here shown the minimum of interwfference between the two is attained. This is because the disturbance due to the higher haromnics of the telegraph impulses generated bythe transmitter do not reach the telephone receiver except after attenuation due to traversing the length of the line.

The advantage is very marked where the telegraph branch joins the main line between amplifiers one of which is adjacent to the telephone receiver. If outgoing impulses are put upon such a branch the higher harmonics are amplified and may reach the telephone receiver in such volume as to be very objectionable. 7

It will be understood that the invention is not limited to the details of the circuit arrangement herein described, as it is obvious that many modifications may be made within the scope of the appended claims, and without departing from the spirit of the invention.

What claimed is: 1. Ina system wherein the same conductors serve as complete metallic telephone and telegraph channels, the combination of two pairs of conductors, a branch from each pair leading to a telephone instrument, a branch leading from each pair to a telegraph instrument, and like branches being phantomed to provide a third channel for each kind of instrument, a high pass filter connected in the telephone branches of said conductors whose shunt elements are provided with mid or neutral points, means for electrically uniting said mid or neutral points, low pass filters connected in the telegraph branches of said conductors whose shunt elements are provided with mid or neutral points and means for electrically uniting said last mentioned mid or neutral points.

2. In combination, two pairs of conductors, each pair being branched to provide a telephone and a telegraph channel over the same conductors, a phantom circuit formed on both telephone and telegraph branches of the two pairs, a high pass filter in each telephone branch composed of series capacities and shunt inductance and alow pass filter for each telegraph branch composed of series inductances and shunt capacities, the shunt elements in each filter being composed of two parts connected in series with each other and capable of functioning independently,

and means for electrically uniting the two high pass filters and for electrically uniting the two low pass filters at the points where the halves of their respective shunt elements are joined.

3. The method of composite signaling which consists in transmitting the telephone currents in one direction only over a pair of conductors, and concurrently transmitting telegraph currents over the same pair of conductors in one direction only, and in the same direction as the telephone currents with respect to either conductor of the pair.

at. In a signaling system a telephone transmission line arranged for one way transmission only of telephone currents, means for transmitting telegraph currents over the said line in one direction only and in the same direction as the telephone currents, and selective circuits comprising inductance and capacity located respectively in the telephone and telegmph branches of the circuit, the values of inductances and capacities being sufiicient to separate the relatively weak received telephone and telegraph impulses into their respective circuits, selective circuits at the transmitting end of the line consisting of inductance and capacity. and located respectively in the telephone and telegraph transmitting branches, said inductances and capacities having values suificient to prevent the relatively strong telephone or telegraph transmitted impulses from entering the sending circuit of the other kind, and to prevent the higher harmonies of the telegraph impulses from interfering with the telephone transmission.

5. In a signaling system, two pairs of conductors arranged to provide two side and one phantom circuit for telephone currents and the tele raph currents and means common to both is e side and phantom circuits for separating the telephone and telegraph currents.

In testimony whereof I have si ed my 10 name to this specification this tent day of February, 1919.

HAROLD S. OSBORNE. 

